U.S. patent application number 15/526099 was filed with the patent office on 2017-11-16 for heat-dissipating structure and method for manufacturing same.
This patent application is currently assigned to Contec Co., Ltd.. The applicant listed for this patent is Contec Co., Ltd.. Invention is credited to Tadashi KAWANO.
Application Number | 20170330817 15/526099 |
Document ID | / |
Family ID | 56074312 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170330817 |
Kind Code |
A1 |
KAWANO; Tadashi |
November 16, 2017 |
HEAT-DISSIPATING STRUCTURE AND METHOD FOR MANUFACTURING SAME
Abstract
A heat-dissipating structure including a heat sink having a
recessed portion on a first surface facing a heat generator, the
recessed portion having a side surface; a heat block fit into the
recessed portion, the heat block having a bottom surface and a side
surface; and thermally conductive grease in contact with both of
the side surface of the recessed portion and the side surface of
the heat block, wherein the bottom surface of the heat block is in
contact with the heat generator.
Inventors: |
KAWANO; Tadashi;
(Nishiyodogawa-ku, Osaka-shi, Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Contec Co., Ltd. |
Nishiyodogawa-ku, Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
Contec Co., Ltd.
Nishiyodogawa-ku, Osaka-shi, Osaka
JP
|
Family ID: |
56074312 |
Appl. No.: |
15/526099 |
Filed: |
November 20, 2015 |
PCT Filed: |
November 20, 2015 |
PCT NO: |
PCT/JP2015/082769 |
371 Date: |
May 11, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2924/14 20130101;
H01L 23/40 20130101; H01L 23/3677 20130101; H01L 2924/0002
20130101; H01L 23/427 20130101; H01L 2924/00 20130101; H05K 7/20
20130101; H01L 2924/0002 20130101; H01L 23/3675 20130101 |
International
Class: |
H01L 23/40 20060101
H01L023/40; H01L 23/427 20060101 H01L023/427 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2014 |
JP |
2014-240675 |
Claims
1-6. (canceled)
7. A heat-dissipating structure comprising: a heat sink having a
recessed portion on a first surface facing a heat generator, the
recessed portion having a bottom surface and a side surface; a heat
block fit into the recessed portion, the heat block having a top
surface, a bottom surface, and a side surface; thermally conductive
grease in contact with both of the side surface of the recessed
portion and the side surface of the heat block; and a thermally
conductive sheet in contact with both of the bottom surface of the
recessed portion and the top surface of the heat block, wherein the
bottom surface of the heat block is in contact with the heat
generator.
8. The heat-dissipating structure according to claim 7, wherein the
recessed portion and the heat block are each shaped like a cylinder
having a central axis perpendicular to the first surface of the
heat sink.
9. A method for manufacturing a heat-dissipating structure
comprising a heat sink having a recessed portion on a first surface
facing a heat generator, and a heat block fit into the recessed
portion, the method comprising: applying thermally conductive
grease to at least one of a side surface of the recessed portion
and a side surface of the heat block; and fitting the heat block
into the recessed portion while rotating the heat block about a
central axis of the heat block with a thermally conductive sheet
provided between a bottom surface of the recessed portion and a top
surface of the heat block such that the heat sink and the thermally
conductive sheet are in contact with each other and the thermally
conductive sheet and the heat block are in contact with each
other.
10. The method for manufacturing the heat-dissipating structure
according to claim 9, further comprising forming the recessed
portion on the first surface of the heat sink by spot facing.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat-dissipating
structure that dissipates heat from a heat generator to the
outside.
BACKGROUND ART
[0002] As a configuration example of a known heat-dissipating
structure of the related art, FIG. 9 shows a heat-dissipating
structure 3 including a heat sink 70, a heat block 20, and a
thermally conductive sheet 60 interposed between the heat sink 70
and the heat block 20. The heat block 20 of the heat-dissipating
structure 3 is in contact with a heat generator 50 provided on, for
example, a printed circuit board 40. Thus, heat generated by the
heat generator 50 is dissipated to the outside along a heat
dissipation route HR2 where the heat from the heat generator 50
sequentially passes through the heat block 20, the thermally
conductive sheet 60, and the heat sink 70.
[0003] In this configuration, the thermally conductive sheet 60
accommodates dimensional tolerances in the thickness direction of
the components and erection tolerances between the components. In
this case, the tolerances mean variations caused by small
undulations or slopes on the surfaces of the components and
machining/assembly. The accommodation of these tolerances secures
adhesion between the heat sink 70 and the heat block 20.
[0004] As shown in FIG. 10, Patent Literature 1 discloses a
heat-dissipating structure 4 including a heat sink 80 having a
projecting portion and a thermally conductive sheet 60 in contact
with the projecting portion of the heat sink 10. In this
configuration, a through hole is formed on a printed circuit board
40 and the projecting portion of the heat sink 80 is fit into the
through hole of the printed circuit board 40, locating the
thermally conductive sheet 60 between the heat generator 50 and the
projecting portion of the heat sink 80. Thus, heat generated by the
heat generator 50 is dissipated to the outside along a heat
dissipation route HR3 where the heat from the heat generator 50
sequentially passes through the thermally conductive sheet 60 and
the heat sink 80.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Patent Laid-Open No.
2005-327940
SUMMARY OF INVENTION
Technical Problem
[0006] In such a configuration, the thermal conductivity of a
thermally conductive sheet is typically lower than those of a heat
sink and a heat block. Moreover, as described above, the thermally
conductive sheet accommodates dimensional tolerances in the
thickness direction of the components and erection tolerances
between the components, requiring at least a certain thickness. In
the configuration of the heat-dissipating structure of the related
art, heat from the heat generator is always dissipated to the
outside through the thermally conductive sheet. This
disadvantageously reduces the heat dissipation efficiency of the
heat-dissipating structure.
[0007] On the other hand, if the thermally conductive sheet is not
used, the tolerances cannot be accommodated and thus adhesion
decreases between the heat sink and the heat block, thereby
reducing the heat dissipation efficiency of the heat-dissipating
structure. Moreover, the thermally conductive sheet may be replaced
with thermally conductive grease having a larger thermal
conductivity than the thermally conductive sheet. However, the
thermally conductive grease cannot sufficiently secure adhesion
between the heat sink and the heat block because of large
dimensional tolerances in the thickness direction.
[0008] Also in the configuration of the heat-dissipating structure
described in Patent Literature 1, the thermally conductive sheet is
used and heat generated from the heat generator is dissipated to
the outside through the thermally conductive sheet, resulting in
the same problem.
[0009] An object of the present invention is to improve heat
dissipation efficiency as compared with a heat-dissipating
structure of the related art.
Solution to Problem
[0010] A heat-dissipating structure of the present invention
includes a heat sink having a recessed portion on a first surface
facing a heat generator, the recessed portion having a side
surface; a heat block fit into the recessed portion, the heat block
having a bottom surface and a side surface; and thermally
conductive grease in contact with both of the side surface of the
recessed portion and the side surface of the heat block, wherein
the bottom surface of the heat block is in contact with the heat
generator.
Advantageous Effect of Invention
[0011] The heat-dissipating structure of the present invention can
improve heat dissipation efficiency as compared with the
heat-dissipating structure of the related art.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a perspective view showing a heat-dissipating
structure according to a first embodiment of the present
invention.
[0013] FIG. 2 is a cross-sectional view taken along line X-XX of
the heat-dissipating structure.
[0014] FIG. 3 is a cross-sectional view showing a heat-dissipating
structure according to a second embodiment of the present
invention.
[0015] FIG. 4 is a cross-sectional view showing a step of a method
for manufacturing the heat-dissipating structure according to the
present invention.
[0016] FIG. 5 is a cross-sectional view showing a step of the
method for manufacturing the heat-dissipating structure.
[0017] FIG. 6 is a cross-sectional view showing a step of the
method for manufacturing the heat-dissipating structure.
[0018] FIG. 7 is a cross-sectional view showing a step of the
method for manufacturing the heat-dissipating structure.
[0019] FIG. 8 is a cross-sectional view showing a heat-dissipating
structure according to another embodiment of the present
invention.
[0020] FIG. 9 is a cross-sectional view showing a heat-dissipating
structure of the related art.
[0021] FIG. 10 is a cross-sectional view showing a heat-dissipating
structure of the related art.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0022] Referring to FIGS. 1 and 2, a heat-dissipating structure
according to a first embodiment of the present invention will be
described below. As shown in FIGS. 1 and 2, a heat-dissipating
structure 1 according to the first embodiment of the present
invention includes a heat sink 10, a heat block 20, and thermally
conductive grease 30. A heat generator 50 provided on, for example,
a printed circuit board 40 is in contact with the heat block 20 and
thus heat generated by the heat generator 50 can be dissipated from
the heat sink 10. The constituent elements of the heat-dissipating
structure 1 will be specifically described below.
[0023] The heat sink 10 has a first surface 11 facing the heat
generator 50. The first surface 11 has a recessed portion 12. The
recessed portion 12 has a side surface 51 and a bottom surface B1.
Specifically, the recessed portion 12 has a cylindrical shape with
a central axis A1 perpendicular to the first surface 11 of the heat
sink 10. Moreover, a fin 14 is provided on a second surface 13
opposite to the first surface 11 of the heat sink 10. The fin 14
provided on the second surface 13 of the heat sink 10 increases the
surface area of the heat sink 10, thereby improving the heat
dissipation efficiency of the heat-dissipating structure 1.
However, the present invention is not limited to the configuration
including the fin on the second surface 13 of the heat sink 10.
[0024] The heat block 20 has a top surface T2, a side surface S2,
and a bottom surface B2. Specifically, the heat block 20 has a
cylindrical shape with a central axis A2 perpendicular to the first
surface 11 of the heat sink 10. The heat block 20 is fit into the
recessed portion 12 of the heat sink 10. The bottom surface B2 of
the heat block 20 is in contact with the heat generator 50. The
heat block 20 in contact with the heat generator 50 can temporarily
dissipate heat from the heat generator 50 to the heat block 20,
thereby preventing heat emitted from the heat generator 50 itself
from persisting so as to damage the heat generator 50.
[0025] The thermally conductive grease 30 is interposed between the
side surface S1 of the recessed portion 12 and the side surface S2
of the heat block 20. In other words, the thermally conductive
grease 30 is in contact with both of the side surfaces S1 and S2.
This configuration can improve adhesion between the side surface S1
of the recessed portion 12 and the side surface S2 of the heat
block 20. The thermally conductive grease 30 is paste that can be
easily deformed. For example, the thickness of the thermally
conductive grease 30 can be larger than 0 [mm] and smaller than or
equal to 0.3 [mm]. In order to improve adhesion between the heat
generator 50 and the bottom surface B2 of the heat block 20,
thermally conductive grease is preferably provided also between the
heat generator 50 and the heat block 20. The thermally conductive
grease 30 is made of, for example, silicon and has a thermal
conductivity of 3.0 [W/(mK)]. Metallic particles of silver or the
like may be mixed with the thermally conductive grease 30 to
improve the thermal conductivity.
[0026] With this configuration, heat generated by the heat
generator 50 is dissipated to the outside along a heat dissipation
route HR1 where the heat from the heat generator 50 sequentially
passes through the heat block 20, the thermally conductive grease
30, and the heat sink 10. This can improve heat dissipation
efficiency as compared with the heat-dissipating structure of the
related art, which will be specifically discussed below.
[0027] In the configurations of the heat-dissipating structure of
the related art, as shown in FIG. 9, the heat sink 10 does not have
a recessed portion while the heat sink 70 is in contact with the
heat block 20 with a thermally conductive sheet 60 interposed
between the heat sink 70 and the heat block 20. Thus, heat
generated from the heat generator 50 is always dissipated to the
outside through the thermally conductive sheet 60.
[0028] The thermal conductivity of the thermally conductive sheet
60 is typically lower than that of the heat sink 10 and the heat
block 20. For example, the heat sink 10 and the heat block 20 are
made of materials such as copper and aluminum. The thermal
conductivity of copper is 398 [W/(mK)] while the thermal
conductivity of aluminum is 236 [W/(mK)]. The thermally conductive
sheet 60 made of materials such as silicon having a thermal
conductivity of 2.3 [W/(mK)].
[0029] Further, the thermally conductive sheet 60 accommodates
dimensional tolerances in the thickness direction of the
components, specifically, the dimensional tolerance of the
thickness of the heat sink 10, the dimensional tolerance of the
thickness of the heat block 20, the dimensional tolerance of the
thickness of the heat generator 50, and the dimensional tolerance
of the thickness of the printed circuit board 40. The thermally
conductive sheet 60 also accommodates erection tolerances between
the components, specifically, an erection tolerance between the
printed circuit board 40 and the heat generator 50 and an erection
tolerance between the heat generator 50 and the heat block 20. This
can secure adhesion between the heat sink 10 and the heat block 20.
In order to accommodate these tolerances, the thermally conductive
sheet 60 needs to have at least a certain thickness and a certain
degree of elasticity.
[0030] For example, the thickness of the heat sink 70 has a
dimensional tolerance of 0.05 [mm], the thickness of the heat block
20 has a dimensional tolerance of 0.05 [mm], the thickness of the
heat generator 50 has a dimensional tolerance of 0.1 [mm], the
thickness of the printed circuit board 40 has a dimensional
tolerance of 0.05 [mm], an erection tolerance between the printed
circuit board 40 and the heat generator 50 is 0.05 [mm], and an
erection tolerance between the heat generator 50 and the heat block
20 is 0.1 [mm]. The sum of the tolerances is 0.4 [mm]. For example,
thermally conductive grease that is larger than 0 [mm] and smaller
than or equal to 0.3 [mm] in thickness cannot sufficiently
accommodate such large tolerances and thus the thermally conductive
sheet 60 having a thickness of, for example, 2.0 [mm] is used
instead. The thermally conductive sheet 60 is compressed into a
thickness of, for example, 1.6 [mm] between the heat sink 70 and
the heat block 20.
[0031] In this case, a heat transfer amount is used as an index
indicating the heat dissipation efficiency of the heat-dissipating
structure. A heat transfer amount is a heat amount that moves from
one surface to the other surface of an object. As indicated by
expression 1 below, a heat transfer amount is proportionate to an
object area. A, a thermal conductivity C of the object, and a
temperature difference D between both surfaces of the object, and
is inversely proportionate to an object thickness B.
E=A/B.times.C.times.D expression 1
where A is an area [m.sup.2], B is a thickness [m], C is a thermal
conductivity [W/(m/K)], D is a temperature difference [K], and E is
a heat transfer amount [W].
[0032] In the configuration of the heat-dissipating structure 3 of
the related art, the thermally conductive sheet 60 is interposed
between the heat sink 70 and the heat block 20, and thus a heat
transfer amount from the heat sink 70 to the heat block 20 is equal
to that of the thermally conductive sheet 60. The heat transfer
amount of the thermally conductive sheet 60 will be examined
below.
[0033] The thermally conductive sheet 60 having a diameter of 14
[mm] has an area of about 154 [mm.sup.2]. If the thermally
conductive sheet 60 has a thickness of 1.6 [mm], a thermal
conductivity of 2.3 [W/(mK)], and a temperature difference of 20
[K] between both surfaces of the thermally conductive sheet 60, the
thermally conductive sheet 60 has a heat transfer amount of 4.42
[W] according to expression 1.
[0034] In the heat-dissipating structure 1 of the present
embodiment, the recessed portion 12 is provided on the first
surface 11 of the heat sink 10 while the side surface S1 of the
recessed portion 12 is in contact with the side surface S2 of the
heat block 20 with the thermally conductive grease 30 interposed
between the side surface S1 and the side surface S2. Thus, a heat
transfer amount from the heat sink 10 to the heat block 20 is equal
to that of the thermally conductive grease 30. The heat transfer
amount of the thermally conductive grease 30 will be examined
below.
[0035] If the top surface T2 of the heat block 20 has a diameter of
14 [mm] and the heat block 20 in contact with the recessed portion
12 of the heat sink 10 has a height of 3.8 [mm], the thermally
conductive grease 30 between the heat sink 10 and the heat block 20
has an area of 167 [mm.sup.2]. Moreover, the thermally conductive
grease 30 for improving adhesion between the heat sink 10 and the
heat block 20 like the thermally conductive sheet has a thickness
of 0.1 [mm], which is smaller than that of the thermally conductive
sheet. If the thermally conductive grease 30 has a thermal
conductivity of 3.0 [W/(mK)] and a temperature difference is 20 [K]
between both surfaces of the thermally conductive grease 30, the
thermally conductive grease 30 has a heat transfer amount of 100.23
[W] according to expression 1.
[0036] In a comparison between the heat transfer amounts of the
thermally conductive grease 30 and the thermally conductive sheet
60 of the related art, it is found that the heat transfer amount of
the thermally conductive grease 30 is at least 22 times as large as
that of the thermally conductive sheet 60, though the thermally
conductive grease 30 and the thermally conductive sheet 60 have the
same area and the same surface temperature difference. This is
because the thermally conductive sheet 60 has a thermal
conductivity of 2.3 [W/(mK)] while the thermally conductive grease
30 has a larger thermal conductivity of 3.0 [W/(mK)], and the
thermally conductive sheet 60 has a thickness of 1.6 [mm] while the
thermally conductive grease 30 has a much smaller thickness of 0.1
[mm].
[0037] In the heat-dissipating structure of the related art, the
heat sink not provided with the recessed portion is in contact with
the heat block so as to dissipate heat, whereas the
heat-dissipating structure 1 according to the present embodiment of
the present invention is configured such that the side surface S1
of the recessed portion 12 of the heat sink 10 is in contact with
the side surface S2 of the heat block 20 so as to dissipate heat.
Thus, the heat dissipation of the heat-dissipating structure 1 is
affected by tolerances in the radial direction instead of
tolerances in the thickness direction.
[0038] As described above, the sum of the tolerances in the
thickness direction is, for example, 0.4 [mm], whereas a
dimensional tolerance in the radial direction of the recessed
portion 12 is, for example, 0.1 [mm] and the dimensional tolerance
in the radial direction of the heat block 20 is, for example, 0.1
[mm]. The total tolerance in the radial direction is no more than
0.2 [mm].
[0039] The accommodation of such small tolerances does not need a
thermally conductive sheet having at least a certain thickness. For
example, only the provision of the thermally conductive grease 30,
which is larger than 0 [mm] and smaller than or equal to 0.3 [mm]
in thickness, secures adhesion between the heat sink 10 and the
heat block 20.
[0040] In the related art, heat is dissipated through the top
surface T2 of the heat block 20, whereas in the heat-dissipating
structure 1 of the first embodiment, heat is dissipated at least
through the side surface S2 of the heat block 20. The heat
dissipation efficiency also depends on a contact area between the
heat block 20 and the heat sink 10. In order to increase the area
of the top surface T2 of the heat block 20, a mounting area on the
printed circuit board 40 needs to be extended. In addition to an
increase in the area of the top surface T2 of the heat block 20, an
increase in the height of the side surface S2 of the heat block 20
and the depth of the recessed portion 12 can extend the area of the
side surface of the heat block 20 opposed to the side surface S1 of
the recessed portion 12 of the heat sink 10. Thus, as compared with
the related art, the heat-dissipating structure 1 of the present
embodiment can easily increase a contact area between the heat
block 20 and the heat sink 10, thereby facilitating improvement of
heat dissipation efficiency.
[0041] As described above, the heat-dissipating structure 1
according to the present embodiment of the present invention can
improve heat dissipation efficiency as compared with the
heat-dissipating structure of the related art. In particular, a
fanless heat-dissipating structure can also sufficiently obtain
heat dissipation efficiency. However, the present invention is not
limited to a fanless heat-dissipating structure. The provision of a
fan can further increase heat dissipation efficiency.
Second Embodiment
[0042] Referring to FIG. 3, a heat-dissipating structure according
to a second embodiment of the present invention will be described
below. A heat-dissipating structure 2 according to the second
embodiment of the present invention is different from that of the
first embodiment in the provision of a thermally conductive sheet
60. Other constituent elements are identical to those of the first
embodiment and thus the explanation thereof is omitted. The
thermally conductive sheet 60 will be specifically discussed
below.
[0043] The thermally conductive sheet 60 is in contact with a
bottom surface B1 of a recessed portion 12 and a top surface T2 of
a heat block 20. In other words, the thermally conductive sheet 60
is interposed between the bottom surface B1 of the recessed portion
12 of a heat sink 10 and the top surface T2 of the heat block 20.
The thermally conductive sheet 60 has a thermal conductivity of,
for example, 2.3 [W/(mK)]. The thermally conductive sheet 60
accommodates the dimensional tolerances of components in the
thickness direction of the heat sink 10 and erection tolerances
between the components. In order to accommodate these tolerances,
the thermally conductive sheet 60 has at least a certain thickness
and a certain degree of elasticity. The thermally conductive sheet
60 having a thickness of, for example, 2.0 [mm] is compressed into
a thickness of, for example, 1.6 [mm] between the bottom surface B1
of the recessed portion 12 and the top surface T2 of the heat block
20. Thus, the heat-dissipating structure 2 of the present
embodiment can obtain adhesion between the bottom surface B2 of the
recessed portion 12 of the heat sink 10 and the top surface T2 of
the heat block 20.
[0044] According to the heat-dissipating structure 2 of the present
embodiment, as in the heat-dissipating structure of the first
embodiment, heat generated by a heat generator 50 is dissipated to
the outside along a heat dissipation route HR2 where the heat from
the heat generator 50 sequentially passes through the heat block
20, the thermally conductive sheet 60, and the heat sink 10 as in
the heat-dissipating structure of the related art, in addition to a
heat dissipation route HR1 where the heat from the heat generator
50 sequentially passes through the heat block 20, thermally
conductive grease 30, and the heat sink 10.
[0045] Thus, in the heat-dissipating structure 2 of the present
embodiment, a heat transfer amount from the heat block 20 to the
heat sink 10 is equal to the sum of the heat transfer amount of the
thermally conductive grease according to the first embodiment and
the heat transfer amount of the thermally conductive sheet of the
related art. For example, as described in the first embodiment, if
the thermally conductive grease 30 has a heat transfer amount of
100.23 [W] and the thermally conductive sheet 60 has a heat
transfer amount of 4.42 [W], a heat transfer amount from the heat
block 20 to the heat sink 10 is 104.65 [W] according to the second
embodiment. Thus, the heat-dissipating structure 2 of the second
embodiment can obtain higher heat dissipation efficiency than the
heat-dissipating structure of the first embodiment.
[0046] In the second embodiment, the thermally conductive sheet 60
interposed between the bottom surface B1 of the recessed portion 12
and the top surface T2 of the heat block 20 presses the heat block
20 and the heat generator in the thickness direction. This can
improve adhesion between the heat generator 50 and the heat block
20 as compared with the first embodiment where the thermally
conductive sheet is not used.
[0047] In the first embodiment, the thermally conductive sheet 60
is not provided between the bottom surface B1 of the recessed
portion 12 of the heat sink 10 and the top surface T2 of the heat
block 20 and thus the bottom surface B1 and the top surface T2 are
not bonded to each other in the thickness direction. Hence, a large
heat transfer amount cannot be expected but at least a certain heat
transfer amount is transmitted in the thickness direction. As
described in the second embodiment, the thermally conductive sheet
60 interposed between the bottom surface B1 and the top surface T2
can bond the bottom surface B1 and the top surface T2 in the
thickness direction, thereby increasing a heat transfer amount.
Third Embodiment
[0048] Referring to FIGS. 4 to 7, a third embodiment of the present
invention will describe an example of a method for manufacturing
the heat-dissipating structure according to the first and second
embodiments of the present invention. First, as shown in FIG. 4, a
heat sink 10 is prepared with a fin 14 formed on a second surface
13. In this configuration, as described above, the fin 14 may not
be formed on the second surface 13 of the heat sink 10.
[0049] Subsequently, as shown in FIG. 5, a recessed portion 12 is
formed on the first surface 11 of the heat sink 10. In this case,
if the recessed portion 12 is formed along with the molded heat
sink 10, it may be difficult to control a dimensional tolerance in
a radial direction of the recessed portion 12. Thus, the recessed
portion 12 is additionally formed after the heat sink 10 is molded.
This can easily control a dimensional tolerance in the radial
direction of the recessed portion 12 and change the dimensional
tolerance according to the location or size of the recessed portion
12 when necessary. For example, after the heat sink 10 is molded
without the recessed portion 12 on the first surface 11, the
recessed portion 12 may be formed on the first surface 11 by spot
facing. However, the recessed portion of the present invention is
not always formed by spot facing. Alternatively, the heat sink
initially provided with the recessed portion may be molded. In this
case, the recessed portion is formed concurrently with the molding
of the heat sink. This can omit the step of additionally forming
the recessed portion, thereby reducing the number of manufacturing
steps.
[0050] As shown in FIG. 6, in the manufacturing of the
heat-dissipating structure according to the second embodiment, the
thermally conductive sheet 60 is provided on the bottom surface B1
of the recessed portion 12 of the heat sink 10. However, the
thermally conductive sheet 60 does not always need to be provided
on the bottom surface B1 of the recessed portion 12 and thus may be
provided between the bottom surface B1 of the recessed portion 12
and the top surface T2 of the heat block 20. For example, the
thermally conductive sheet 60 may be provided on the top surface of
the heat block 20. This step is not performed in the manufacturing
of the heat-dissipating structure according to the first
embodiment.
[0051] Finally, as shown in FIG. 7, the heat block 20 is fit into
the recessed portion 12. Before the heat block 20 is fit, the
thermally conductive grease 30 is applied to the side surface S2 of
the heat block 20. This brings the heat block 20 into contact with
the side surface S1 of the recessed portion 12 with the thermally
conductive grease 30 interposed between the side surface S1 and the
side surface S2. The thermally conductive grease 30 may be applied
to the side surface S1 of the recessed portion 12 instead of the
side surface S2 of the heat block 20 or may be applied to both side
surfaces S1 and S2.
[0052] If the thermally conductive sheet 60 is provided to
manufacture the heat-dissipating structure of the second
embodiment, the heat sink 10 and the thermally conductive sheet 60
are placed in contact with each other and the thermally conductive
sheet 60 and the heat block 20 are placed in contact with each
other. In other words, the bottom surface B1 of the recessed
portion 12 and the top surface T2 of the heat block 20 are placed
in contact with each other with the thermally conductive sheet 60
interposed between the bottom surface B1 and the top surface
T2.
[0053] In this configuration, the heat block 20 is desirably fit
into the recessed portion 12 while rotating about the cylindrical
axis of the heat block 20, which will be specifically described
below. In order to fit the heat block 20 into the recessed portion
12 of the heat sink 10, a dimensional difference is necessary
between the diameters of the heat block 20 and the recessed portion
12. Specifically, the heat block 20 is slightly smaller in diameter
than the recessed portion 12. Since the heat block 20 is inserted
into the recessed portion 12 while being rotated, the heat block 20
is easily inserted even if the dimensional difference between the
diameters of the recessed portion 12 and the heat block 20 is
minimized. For example, the recessed portion 12 has a diameter of
14.2 [mm] and the heat block 20 has a diameter of 14.0 [mm],
resulting in a small dimensional difference of 0.2 [mm]. This can
improve adhesion between the side surface S1 of the recessed
portion 12 of the heat sink 10 and the side surface S2 of the heat
block 20, thereby increasing the heat dissipation efficiency of the
heat-dissipating structure.
[0054] As shown in FIG. 2 or 3, the heat-dissipating structure
configured thus includes the heat generator 50 in contact with the
bottom surface B2 of the heat block 20, thereby dissipating heat
from the heat generator 50 to the outside.
[0055] The recessed portion 12 of the heat sink 10 and the heat
block 20 are, but not exclusively, cylindrical in the first and
second embodiments. For example, even if the recessed portion of
the heat sink and the heat block are shaped like polygonal columns,
the side surface of the heat block is in contact with the side
surface of the recessed portion with the thermally conductive
grease interposed between the side surfaces, achieving higher heat
dissipation efficiency as compared with the heat-dissipating
structure of the related art. In the case of the cylindrical shape,
the heat block can be fit into the recessed portion while being
rotated.
[0056] In the first embodiment, the recessed portion 12 of the heat
sink 10 has the bottom surface B1 and the heat block 20 has the top
surface T2. The present invention is not limited to this
configuration. The recessed portion of the heat sink may not have
the bottom surface and the heat block may not have the top surface.
For example, as shown in FIG. 8, the recessed portion 16 of the
heat sink 15 and the heat block 21 may be conical or pyramidal.
Also in this case, the side surface S2 of the heat block 21 is in
contact with the side surface S1 of the recessed portion 16 of the
heat sink 15 with the thermally conductive grease 30 interposed
between the side surface S1 and the side S2, thereby improving heat
dissipation efficiency as compared with the heat-dissipating
structure of the related art. In the case of a pyramidal or conical
shape, the side surface can have a larger area than that of a
cylinder or a polygonal column, thereby improving the heat
dissipating structure. In the case of a conical shape, the heat
block can be fit into the recessed portion while being rotated.
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